For decades, cougars preyed on sheep from farms along Argentina’s coast, and farmers hunted them — hard. Cougars have disappeared from the landscape. Then, in 2004, conservationists established Monte León National Park in the region. As expected, once the hunting stopped, the big cats returned. And when they returned, they found a new player in their old neighborhood: the Magellanic penguins.
What the scientists didn’t anticipate was that not only would cougars prey on penguins, but that the birds’ seasonal arrival would reorganize the way these solitary cats move, interact and hunt across the landscape. A new study published today in the journal Proceedings of the Royal Society B documents this change in puma behavior for the first time and challenges our assumptions about what happens when large predators return to an ecosystem.
“When we start rewilding the land, returning species might find a system that’s a little different from the one they inhabited 100 years ago – and adapt to it,” says Emiliano Donadio, scientific director at Fundación Rewilding Argentina and co-author of the study.
(How a penguin ‘massacre’ led to historic new protections in Argentina)
Camera traps reveal cougar predation
The researchers did not initially set out to study this unique predator-prey relationship. Lead author and ecologist Mitchell Serota, then at the University of California Berkeley, was working with Fundación Rewilding Argentina to study how wildlife reacts when human pressures are removed from former ranchers. “I went to Patagonia to get a broad understanding of the results of the restoration. Penguins were not the original focus at all,” he says.
In 2023, Serota and his colleagues reported that the big cats were actually feeding on the embarrassed birds. “This interaction was known, but we thought it was minor,” he says. “Maybe just a handful of individuals.”
The team set 32 traps in the park and tracked 14 adult cougars (Cougar concolor) with GPS collars between September 2019 and January 2023. Combining this data with field observations, the researchers quickly realized that cougars were eating penguins much more often than expected.
“We were getting repeated cougar sightings right around the penguin colony,” Serota recalls. “Then it became clear that this was not a secondary note. It was something that was shaping the way these animals used the landscape.”
A new food web is taking shape
Because Magellanic penguins (Spheniscus magellanicus) spending much of their life at sea, they are unusual prey for a large terrestrial carnivore whose diet consists mainly of land mammals such as deer, guanacos (relatives of llamas) and hares. But during their breeding season—roughly September through April—the seabirds flock to land in large numbers. At Monte León, more than 40,000 breeding pairs nest along a coastline approximately two kilometers long.
(What Magellanic penguins teach us about survival)
For a cougar, whose territory can cover hundreds of square kilometers, this creates a strange situation: an extremely abundant food source, concentrated in a very small area and available only for part of the year. The team found that population density remained similar – about 13 cats per 100 square kilometers – whether penguins were present or absent. So the penguins didn’t create more cougars, they reorganized the way these cats share space.
Penguin-eating cougars appear to behave quite differently from those that prefer other diets in Patagonia. The study found that bird-eating big cats shared the same area much more frequently than non-bird-eating cats and did not attack each other as often as expected. “In other words, the penguin-eating cougars were quite tolerant of each other’s presence,” says Donadio, who is also a National Geographic Explorer.
Such tolerance came as a surprise, given the lonely stereotype of cougars. In Patagonia, these big cats are outdoors because they are the top predator. “Unlike in Africa, they don’t need to sneak up together to take down prey twice or three times larger. And unlike in North America, there are no grizzly bears, black bears or wolves, so these cats don’t sneak through the trees at night like they are up here,” says Jim Williams, who has worked for decades as a biologist with Montana Fish and Wildbird, has written about the relationship between Montana Fish and Wildbirds. in his book The Way of the Puma.
In Monte León, cougars often visit the penguin colony in the evening to hunt. Gonzalo Ignazi
To some extent, it makes sense for cougars to pounce on the new food source, since penguins are low-risk prey. “The big cats — lions, panthers, cougars, cougars — always prey on the most abundant and vulnerable food sources available,” says Williams, who was not affiliated with the current study. “This is not shocking from an ecological point of view or from a natural behavior point of view, but it is for people who do not know that penguins and cougars overlap,” he adds.
But the changes in behavior are surprising. “We tend to think of cougars as extremely aggressive and intolerant,” says Donadio. “But when food is plentiful and concentrated, there’s no need to defend it. They become more socially tolerant,” he adds.
(What a photographer learned after spending almost a year with cougars)
Open questions
Donadio says surveys so far suggest the penguin colony has remained stable or even increased since the park was created. What remains uncertain is how the changes in puma behavior driven by the penguins spill over into the rest of the ecosystem—especially guanacos, Patagonia’s dominant herbivore and the puma’s traditional primary prey.
Despite the behavioral changes documented in the study, some important questions remain. Researchers still don’t know how many penguins kill individual pumas, making it difficult to assess the long-term impact of predation on the colony, even though the number of penguins at Monte León appears stable or increasing so far. Nor can I yet determine whether high cougar density is a temporary or long-term feature of the ecosystem.
Researchers also have yet to figure out the broader ecological consequences of penguin-induced changes in cougar behavior. “We know that the penguin colony has changed where, when and how cougars get their food, but the next step is to understand the ecological implications of this change,” says Serota.
For now, findings of cougar behavior prove that when nature is given space, it doesn’t always look back, it improvises. “Restoration is not going back to a historical snapshot,” says Serota. “Species are returning to ecosystems that have changed dramatically. That can create entirely new interactions.”
The nonprofit National Geographic Society, committed to illuminating and protecting the wonder of our world, funded the work of explorer Emiliano Donadio. Learn more about the Society’s support for explorers.